Optimal operation of micro energy networks based on energy hub model

博士留学生学位论文

基于能量枢纽模型的微能源网优化运行

氧化石墨烯调控纳米结构 ZnO 和 TiO2

作者姓名 HA THANH TUNG

学科专业 电力系统及其自动化

指导教师 张勇军 教授

所在学院 电力学院

论 文 提 交 日 期 2018 年 12 月 26 日

Optimal operation of Micro energy networks

based on energy hub model

A Dissertation Submitted for the Degree of Doctor of Philosophy

Candidate：Ha Thanh Tung

Supervisor：Prof. YongJun Zhang

South China University of Technology

Guangzhou, China

分类号：TM71 学校代号：10561

学 号：201512800123

华南理工大学博士学位论文

基于能量枢纽模型的微能源网优化运行

作者姓名：Ha Thanh Tung 指导教师姓名、职称：张勇军 教授

申请学位级别：工学博士 学科专业名称：电力系统及其自动化

研究方向：能源互联网优化运行

论文提交日期：2018 年 12 月 26 日 论文答辩日期：2019 年 03 月 日

学位授予单位：华南理工大学 学位授予日期： 年 月 日

答辩委员会成员：

主席： 蔡泽祥

委员： 吴杰康、管霖、刘明波、张勇军

华南理工大学

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I

摘 要

在当今经济社会活动中，能源发挥着重要的作用。一方面，能源成本是产品价值

的重要影响因素；另一方面，能源的安全和由能源利用所引发的环境问题也促使人类

不断探索节能以及环保的新模式，促进了科学和技术的发展革新。当前针对能源危机

和环境问题，全球科学家重点关注的一个解决方案就是构建能够综合不同类型能源的

能源网络，即综合能源系统。通过综合能源系统增强用户用能的可靠性、减少环境污

染、提高能源综合利用效率，推进社会资源环境的可持续性发展。

能量枢纽（Energy Hub，EH）是构建综合能源系统的一个重要基础。能量枢纽模

型构建了一个可连接各种类型能量，并且可以灵活响应各种负荷需求的微能源系统模

型，适用于居民区以及市中心等负荷集中区。如今，城市化的快速发展导致了负荷的

激增以及负荷使用类型的多样化，同时，先进的可再生能源技术以及存储和转化技术

在提高能源效率方面也取得了重大的进展。因此需要新的研究方案来改进能量枢纽的

结构并且解决多个能量枢纽构建的微能源网模型的最优运行的问题。本文将在能量枢

纽模型的基础上，对综合微能源网的优化运行问题进行分析，本文的主要内容分为以

下三个部分：

1、为突破现有 EH 建模研究的局限性，本文提出了一种扩展 EH 模型，用于提高

住宅区负荷的综合能源利用效率，降低能源使用成本。这个扩展模型考虑到了太阳能

（包括太阳能的光电利用和光热应用）与电池储能系统(Battery energy storage system，

BESS)相结合。在现有的能源价格及满足能源负荷需求的前提下，以一天能源使用总成

本最低为目标，对 EH 中设备及外部供能的功率分配进行优化。约束条件包含了 EH 输

入-输出的能量平衡，设备的容量限制以及 BESS 的荷电状态约束等。仿真算例对比分

析了在不同 EH 结构的情况下，太阳能光电、光热利用和 BESS 对运行调度的影响。结

果表明所提出的模型对优化用户综合用能具有较好的效益，并且，该 EH 结构和运行优

化模型适用于住宅型园区的负荷。

2、EH 的结构特征和优化运行对园区供能特性和可靠性具有重大影响。为了更好

地实现园区的优化供能，通过同时关注 EH 的结构特征和优化运行来协同园区的能源优

化至关重要。由于目前对同时考虑 EH 系统结构及优化运行的联合优化问题缺乏研究，

因此，本文研究着重于建立快速识别系统最优结构并同时满足最优运行两个目标的数

学模型。具体地，本文提出了具有 12 个元件（包括能量输入、转化以及储存元件）的

II

EH 模型。在该优化问题中，采用二进制变量来表示元件使用与否的状态，当二进制变

量为 0 时，代表该元件未被使用，而当二进制变量为 1 时，代表该元件处于使用的状

态中。通过 12 个元件的组合，本文提出了 144 种具有不同能量枢纽结构的优化场景，

并针对不同场景下的能量枢纽最优运行结果进行了比较。在对优化结果进行比较后可

以发现，对结构和运行进行统一优化之后得到的能量枢纽的最优结构与 144 种不同结

构中对运行进行优化后成本最低的结构是相同的。因此，本文所提的数学模型能够快

速准确地同时解决结构和运行的最优化问题。

3、基于对含有多个 EH 优化运行研究的不足，并考虑到可再生能源和储能系统在

微能源网中逐渐广泛应用的场景，本文提出了微能源网络（MEN）的协调优化运行的

方法，该微能源网络包括了光伏、风电、电网和天然气传输网、以及多个 EH。本文引

入了四种不同的运行方案（单纯考虑电力作用、考虑电能和天然气的作用、考虑电力

天然气以及可再生能源的作用、考虑电力天然气可再生能源以及储能共同的作用）来

评估能源类型和储能系统对微能源网性能的影响。求解的结果表明，与传统的单纯电

力供应网络相比，在考虑太阳能，风能和储能系统的能量枢纽基础上构造的能量枢纽

效率更高。

本文采用通用代数建模系统（GAMS）对所建立的数学模型进行求解，本文得到

的结论对构建小规模多能量需求的能源管理模型具有重要的指导意义。

关键词：微能源网；能量枢纽；优化运行；GAMS；BESS；最优结构

III

Abstract

Energy plays an essential role in all social and economic activities with deep engagement.

Energy cost is one of the key-driven factors contributing to industry manufactory and even

other social areas such as culture and politics. Energy security and environmental issues have

facilitated human beings to explore energy-efficient, economical and environment-friendly

models. The energy network, combining various different energy categories, tends to be an

innovative solution that attracts scientists’ eyeball worldwide. Such energy network helps to

enhance reliability, reduce environmental pollution, facilitate technology development in the

energy system and promote energy sustainability. Hereby energy hub (EH) can be used to

build up energy network model.

In terms of micro energy network (MEN), the multi-energy network operation optimization

is analyzed based on the EH model. The solution is applied to the regions with highly

intensive energy consumption, including residential areas, urban areas, etc. Besides, the rapid

urbanization has led to load volume expansion and diversified energy consumption. The

advanced technology of renewables integration, alongside with storage and conversion

sections, has improved energy efficiency. The new research proposal is required to optimize

EH structure and operations of MEN model built up by multiple EH. This dissertation

especially aims to resolve the following key issues:

1/ This thesis presents an extended EH model to optimize total energy use costs for loads in

residential areas, with the aim to fulfill the research gap in EH modeling and improving the

operational efficiency of multiple forms of energy consumption. This extended model

considering the involves solar energy (provided by PV and SHE) combined with Battery

energy storage system (BESS). The optimization problem is set up based on daily load

demand (such as electricity, heat, and cooling) and time-of-use (TOU) energy prices. A

mathematical model is constructed with the objective of optimizing total energy cost during

the day, including some constraints such as input-output energy balance of the EH, electricity

price, capacity limitation of the system, and charge/discharge power of BESS. Four

operational cases based on different EH structures are compared to assess the effect of solar

energy applications and BESS on operational efficiency. The results show that the proposed

IV

model predicts significant changes to the characteristics of electricity and gas power bought

from utilities, leading to reduced total energy cost compared to other cases. They also indicate

that the model is appropriate for the characteristics of residential loads.

2/ The structural and optimal operation of an energy hub has a tremendous influence on the

hub’s performance and reliability. In order to achieve the global optimum conditions for

supplying energy, it is quite essential to develop the optimization research issues by focusing

on hub system structure and operation simultaneously. Based on the lack of study about joint

optimization problem, this research also concentrates on establishing a mathematical model to

rapidly identify the optimal model structure that simultaneously satisfies two objectives:

optimizing operating costs and selecting the optimal operating structure. The objective of the

investigation is to penetrate into this joint optimization problem with a handy calculation

method. This thesis envisions an innovative methodology that prominently increases the

synergy between structural and operational optimization and targets system cost affordability.

The generalized energy system structure is presented theoretically with all selective hub sub￾modules, including electric heater (EHe) and solar sources block sub-modules. To minimize

energy usage cost, an energy hub is proposed that consists of 12 kinds of elements (i.e.,

energy resources, conversion, and storage functions) and is modeled mathematically in a

General Algebraic Modeling System (GAMS), which indicates the optimal hub structure’s

corresponding elements with binary variables (0, 1). Simulation results contrast with 144

various scenarios established in all 144 categories of hub structures, in which for each

scenario the corresponding optimal operation cost is previously calculated. These case studies

demonstrate the effectiveness of the suggested model and methodology.

3/ Previous peer research seldom addresses the problem of multiple EH optimal operations.

Considering integration of renewables and storage systems, the dissertation proposes a

method to coordinate optimal operations in MEN containing electricity and natural gas

networks, based on EH model. The EH can be considered as the grand network node to

contain various categories of energy. The demands for electricity, heat, and cooling load can

be fulfilled with the application of conversion and storage devices. Four different operating

scenarios are established to evaluate how energy sources and storage systems influence MEN.

In comparison to traditional electricity supply, the simulation results indicate that MEN built

V

up by EH, with the integration of solar energy, wind energy and storage systems, is more

efficient.

The General Algebraic Modeling System (GAMS) is applied to solve the optimal operating

problems in this study. The dissertation research contributes to the modeling and calculation

for flexible and efficient energy management, meeting the demand for small-scale loads with

various energy engagement.

Keywords： Micro energy network; Energy Hub; Optimal operation, General algebraic

modeling system (GAMS); Optimal structure.

VI

Table of Contents

摘 要............................................................................................................................................I

Abstract.................................................................................................................................. III

Table of Contents....................................................................................................................VI

Chapter 1 Introduction and Literature review...................................................................... 1

1.1 Motivation .................................................................................................................... 1

1.2 Literature Review......................................................................................................... 5

1.2.1. Micro energy network ........................................................................................ 5

1.2.2. Energy hub ......................................................................................................... 7

1.2.3 Optimal operation of EH................................................................................... 10

1.3 Introduction to GAMS programming language ......................................................... 14

1.3.1．Algorithm and solver MINOS in GAMS programming language................. 16

1.3.2. Algorithm and solver BONMIN GAMS programming language.................... 21

1.4 Research opbjectives.................................................................................................. 22

1.5 Thesis outline ............................................................................................................. 23

Chapter 2 Energy hub modeling to minimise residential energy costs considering solar

energy and BESS .................................................................................................................... 25

2.1 Introduction ................................................................................................................ 25

2.2 Energy hub model for residential area load................................................................ 26

2.2.1 Some energy supply models.............................................................................. 26

2.2.2 The proposed EH model.................................................................................... 27

2.3 Solar and BESS technologies..................................................................................... 30

2.3.1 Solar .................................................................................................................. 30

2.3.2 BESS technology .............................................................................................. 37

2.4 Mathematical model................................................................................................... 39

2.4.1. The objective funcion....................................................................................... 39

2.4.2. Constraints ....................................................................................................... 40

2.5. Simulation Result ...................................................................................................... 43

2.5.1. Database ........................................................................................................... 43

2.5.2 Optimization results.......................................................................................... 46

VII

2.6 Summary .................................................................................................................... 52

Chapter 3 Energy Hub’s Structural and Operational Optimization for Minimal Energy

Usage Costs in Energy Systems............................................................................................. 53

3.1 Introduction ................................................................................................................ 53

3.2 Design of the Model................................................................................................... 54

3.2.1 The Energy System’s Structure ......................................................................... 54

3.2.2 The Structural Optimization of Hub Modeling................................................. 55

3.3 Mathematical Model .................................................................................................. 58

3.3.1.The Objective Function..................................................................................... 58

3.3.2. Constraints ....................................................................................................... 58

3.4 Simulation Result ....................................................................................................... 61

3.4.1. Hub Data Description....................................................................................... 61

3.4.2. Calculation Result............................................................................................ 63

3.4.3. Result Discussions ........................................................................................... 68

3.5. Summary ................................................................................................................... 69

Chapter 4 Optimal operation of micro energy networks.................................................... 77

4.1 Introduction ................................................................................................................ 77

4.2 System modeling ........................................................................................................ 78

4.2.1 The micro energy network based on Energy hub.............................................. 78

4.2.2. Electricity network........................................................................................... 78

4.2.3 Natural network................................................................................................. 79

4.3 The optimal operation models.................................................................................... 81

4.3.1 The proposed model.......................................................................................... 81

4.3.2. Mathematical model......................................................................................... 84

4.4 Simulation results....................................................................................................... 87

4.4.1 Case studies....................................................................................................... 87

4.4.2 Database ............................................................................................................ 88

4.4.3. Calculation result ............................................................................................. 92

4.5 Summary .................................................................................................................... 98

Chapter 5 Conclusion and Future work............................................................................... 99

5.1 Conclusions................................................................................................................ 99

VIII

5.2. Contributions........................................................................................................... 100

5.3 Future work .............................................................................................................. 101

References ............................................................................................................................. 103

List of Publications............................................................................................................... 114

Acknowledgments................................................................................................................. 117

Chapter 1 Introduction and Literature review

1

Chapter 1 Introduction and Literature review

1.1 Motivation

Energy is an important sector in the socio-economic development process. Thus, price

fluctuations, institutions or technological advances in energy exploitation and use always

attract the attention of researchers and policymakers in every country in the world. The 1973

oil crisis was the first bell to warn of potential energy shortages in the future when it was not

being exploited and used effectively. It was the energy fluctuations in this period that altered

the sense of human energy use, changed the way and operating mechanism of the energy

system in the world. In the context of economic globalization and climate change, the issue of

exploitation and optimal use of energy has become increasingly urgent and important.

In the past, forms of energy such as electricity, natural gas, and heat often existed as

single, independent systems[1]. In recent years, with the development of science and

technology, the optimum combination of these types of energy has become a major concern[2-

3]. The concept of energy networks[4-6] is considered as a breakthrough in the following

highlights:

+ In the aspect of energy production, different forms of energy can be transformed,

mutually supportive. For example, for a mixed grid of natural gas and electricity, natural gas

can be converted into electricity or heat. This not only increases operational flexibility but

also increases the reliability of power supply.

+ Regarding energy costs, consumers can choose different energy forms with the lowest

energy costs. For example, cooling needs can use electrical or thermal energy through a

switch from power to cool or from heat to cool.

In general, the goal of the energy network is to satisfy two economic factors and meet

the varied needs of the load. This model enhances reliability, reduces environmental pollution,

improves stability, and achieves energy efficiency and conservation goals.

As technology developed, many power supply models have been researched, applied and

put into practice such as microgrids[7], virtual power plants[8], power supply system’s

quantity[9], intelligent energy system[10]. Among them, the most successful was the EH study,